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Saltwater Aquarium Filtration

Saltwater Aquarium Filtration

Updated February 13, 2015
The type of filtration system you choose for your saltwater aquarium is incredibly important. Learn the basics here.
Once you’ve decided that a saltwater aquarium is the right choice for you, you then need to equip and set up your tank. One of the most important aspects of setting up a saltwater aquarium is choosing a filtration system. Having a good filtration system in place is the key to keeping your tank water clean and clear. If the water quality in your tank is low, your fish will become stressed and they will be more likely to get sick as a result. Bacteria, algae and impurities thrive in poor water conditions making your tank inhabitants susceptible to illness and death. Invertebrates, in particular, will be the first to show the effects of poor quality water.

A good filtration should help to keep ammonia and nitrate levels low enough that they do not have a negative impact on your water quality or on your tank inhabitants. Water movement, or circulation, is another important aspect of saltwater aquarium filtration - adequate water movement should be maintained and provide for good gas exchange. Good water movement and surface aeration also help ensure that the oxygen in the water is dissolved correctly. Warmer water temperatures sometimes prevent this from happening so, if you have a tropical saltwater tank you need to be extra careful about maintaining healthy water circulation or your fish could suffocate. Currents also help to feed and nourish your saltwater tank inhabitants while washing away waste products and sediment that promote damaging algae growth. Fighting against water current also helps your fish burn off the excess fat found in many commercial fish foods.

Before you can select the right filtration system for your saltwater aquarium, you need to understand the basics about filtration. There are three types of filtration that you should be aware of:

1. Mechanical Filtration 
Mechanical filtration is the most basic kind of filtration but it is also one of the most important. A mechanical filtration system separates un-dissolved waste from the water but will not eliminate dissolved waste, bacteria, algae or debris. Mechanical filtration simply involves the removal of suspended particles of waste, excess food, plant matter and general dirt from the aquarium to improve water quality. Most filters employ some sort of mechanical filtration through filter floss, pads or sponges that trap the waste as water passes through it. Water is pushed through a strainer (filter media) which catches all free-floating particles unable to pass through the filter.
2. Chemical Filtration 
One step up from mechanical filtration is chemical filtration. Chemical filtration systems eliminate liquefied impurities from the water – that is, dissolved wastes and toxins that you cannot physically see. Carbon or chemical resins work aggressively to extract toxins from tank water until the filter is saturated. As the filter media becomes saturated with dissolved wastes, it becomes less effective. For this reason, you need to change your chemical filtration media every three to four weeks.

3. Biological Filtration
The third type of filtration is very different from the other two because it doesn’t involve any actual filtration in the literal sense. Rather, biological filtration systems consist of nitrifying bacteria that help to break down wastes in the aquarium. A biological filter is a living entity that takes in oxygen and unwanted substances from the water. Biological filtration is the process in which beneficial bacteria convert organics that have been broken down into the toxic elements of Ammonia and Nitrite into the less harmful compound Nitrate, which can then be removed by water changes or chemical means. The process of Biological filtration does not happen fast – it usually takes between four to six weeks to be established. Another name for biological filtration that you might be familiar with is “cycling” or the nitrogen cycle. In order to ensure a safe and healthy environment for your fish, you need to establish a biological filtration system in your saltwater aquarium before you add your fish. If the system is not in place, the biological load of your tank could be too high for the beneficial bacteria to accommodate and, as a result, ammonia levels will spike and your fish could get sick and die.

Now that you’ve learned the basics about the different types of filtration, you should be able to see how all three of them combine to create an effective filtration system. To achieve the desired results in your own saltwater tank, the three different types of filtration should be used in combination. This is achieved through the use of various media or resins placed in the filter. These media removes dissolved waste materials such as fish waste, etc. that can cause odors and discoloration of the aquarium water. Chemical media placed inside the filter can also remove Phosphates, Nitrates, Ammonia and many other toxins. The most common form of chemical filtration is the use of activated carbon.

With all of this information in mind, you should now take the time to learn about the differen types of filtration systems available for saltwater tanks. Each system has its own unique set of benefits and disadvantages, so keep these things in mind as you consider the needs for your saltwater tank. The most popular types of filtration systems for saltwater aquariums include canister filters, wet/dry filters, and fluidized bed filters. Extra equipment like protein skimmers also play an important role in maintaining good water quality in a saltwater tank.
Canister Filters
This type of filter provides mechanical, chemical, and biological filtration and they are particularly useful for aquariums that are 40 gallons in capacity or larger. Canister filters are multipurpose filters that may be used in conjunction with supplementary filtration equipment or they can work well as the sole filtration device in a saltwater aquarium. A canister filter consists of a plastic housing, or canister, that contains various types of filter media. A siphon tube draws water from the aquarium into the canister, forcing it through the filter media and back into the tank through a flexible pipe. As water is forced through filter media, solid debris is caught and dissolved wastes are filtered out of the water. Biological filtration media inside the filter give beneficial bacteria a surface on which to grow and reproduce.

The main benefit of a canister filter is its power – these filters come in a variety of sizes and they can be customized for your particular tank by using certain types of filter media. Canister filters are a particularly good option if you plan to keep a large number of fish or invertebrates in your tank.  Another benefit of canister filters is that they are completely self-contained which means that you can store them in an aquarium cabinet below or behind the tank – it doesn’t have to hang on the back of the tank like a power filter. In terms of price, canister filters range depending on the size of the filter. To get the maximum benefit for your aquarium, choose a high-quality filter rather than a mediocre filter for the sake of saving money because you’ll just have to replace it sooner.

Wet/ Dry Filters (Trickle Filter)

A Wet/Dry filter, also called a trickle filter, is a great option for saltwater aquariums for a number of reasons. Not only do these filters provide excellent biological filtration, but they can be customized for your particular tank by adding different types of filter media and supplemental equipment to a sump system. Setting up a sump system for your wet/dry filter can be a lot of work but, once you have it up and running, it will basically maintain itself. Like a canister filter, a sump system with a wet/dry filter can be housed below the tank in an aquarium cabinet and siphon tubes can be used to transport water back and forth between the tank and the filter.

Wet/dry filters typically utilize organic filter media such as bioballs or floss located within the filter itself to accommodate biological filtration. Water trickles over the media and creates a large air-to-water surface attracting debris to the structure of the media. The addition of activated carbon or other chemical filtration media can facilitate the removal of dissolved wastes from tank water and sponges and other mechanical filtration media can facilitate the removal of solid wastes. Another thing you might add to your sump system is an overflow tank – this is simply a tank that has extra water in it which prevents your tank from overflowing. Having one of these tanks also makes water changes much easier because you simply add fresh water to the tank and it will be added to the filtration system.

Though there are many benefits to using wet/dry filters there are also some downsides that you should consider. Often referred to as nitrate factories, many aquarists believe that wet/dry filters are suitable for fish-only tanks but not reef systems. Over time, the bio-material inside the wet/dry chamber becomes dirty which eventually leads to a build-up of unwanted nitrates in the aquarium and, as you should know, nitrates are not reef friendly! If you perform routine maintenance on your wet/dry filter, however, and keep up with your regular water changes, then this might not be a problem.

Fluidized Bed Filters
A fluidized bed filter differs from canister filters and wet/dry filters in several ways. The most notable difference is the fact that these filters hang on the back of the tank. Fluidized bed filters work by pumping tank water into the filter, forcing it up through filter media consisting of sand, silica chips, or plastic. In order to facilitate filtration, you will probably need to buy a separate power filter or pump – most fluidized bed filters do not come with one. The benefit of this type of filter is that it provides great surface area for beneficial bacteria to grow. A downside is that the sand will eventually compact which will restrict airflow and it could reduce oxygen levels in the tank. Another downside is the fact that chemical filtration typically doesn’t work well with a fluidized bed filter.

Fluidized bed filters are one of the best choices for planted aquariums because the filter will not drive off valuable CO2, yet it is efficient and very low maintenance. Although the bacterial bed takes longer to establish, once it is set up it does not have to be disturbed when performing maintenance, as other filtration systems must. Relatively new, these filters are very efficient biological filters utilizing sand as the filter medium. The small particles provide a high surface area for the bacterial colonies. Although it takes a bit longer to mature initially, the fluidized bed is an excellent biological filter that can be used in any sized aquarium. One thing to keep in mind with these filters, however, is that they can be expensive. A high-quality option may cost you between $50 and $150, and that doesn’t include the price of the pump you need to power it.

Protein Skimmers

Also referred to as "foam fractionators" or "absorptive foam separators," protein skimmers work by removing organic compounds from the water by means of air bubbles that bring waste to the tank surface. The foam that is produced is then deposited into an enclosed compartment. This type of filtration is mainly utilized in reef tanks and it eliminates liquefied impurities before they can decompose in the tank. Each type of protein skimmer has its own good and bad points, but the bottom line is that you have to know where you are going to put the skimmer. In-tank skimmers are the least expensive but offer the fewest options. The in-sump models offer the most features, but are among the most expensive. The models that hang on the side of the tank are by far the most popular due to their reasonable prices and easy installation.

Having reviewed the three different types of filtration and the most popular filter options, you should now be equipped to decide on a filtration system for your saltwater aquarium. Your filtration system's function is to reduce the amount & effects of wastes in tank water and to stabilize the water chemistry. Choosing the right filter will ultimately come down to the size of the tank, the type of tank and the livestock that will inhabit it. Check with your local pet store to find out what will work best for the tank that you have in mind. 

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